The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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Mounjaro weight loss injections — NHS and UK Prescribing Context
"weight loss injections" is the colloquial UK term for prescription weight loss injections like Mounjaro (tirzepatide). Mounjaro is a once-weekly injectable medicine licensed in the UK for weight management in adults with obesity or overweight and weight-related health conditions. It's a prescription-only medicine that works by activating two natural hormone pathways — GIP and GLP-1 — to help regulate appetite and support feeling fuller after meals. Access in the UK is available through NHS specialist weight management services or privately through a licensed prescriber. This guide explains NHS eligibility criteria, NICE approval, and how to access Mounjaro in the UK. Our free GLP-1 weight loss calculator can help you understand potential outcomes at different doses.
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Calculate Your BMI Instantly
Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
NHS Eligibility and NICE Guidance for Mounjaro
NICE has approved tirzepatide (Mounjaro) for use within NHS specialist weight management services, making it available to eligible adults in England, Wales, Scotland, and Northern Ireland. However, NHS access is limited to tier 3 and tier 4 specialist services — your GP cannot prescribe it directly in primary care.
You may be eligible for Mounjaro on the NHS if you have:
- A BMI of 30 kg/m² or above (obesity), OR
- A BMI of 27–29.9 kg/m² with at least one weight-related health condition (type 2 diabetes, prediabetes, hypertension, dyslipidaemia, obstructive sleep apnoea, or cardiovascular disease)
- Lower thresholds may apply if you are of South Asian, Chinese, Black African, or Black Caribbean heritage due to higher cardiovascular and metabolic risk at lower BMI levels
You'll need a GP referral to a specialist weight management service in your area. Waiting times vary significantly by region (ICB). Once assessed, a prescriber will determine if Mounjaro is suitable for your individual circumstances, medical history, and current medications.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
NHS vs Private Access — Routes to Getting Mounjaro
NHS route: Referral from your GP to a tier 3 specialist weight management service. Free on prescription once approved, but waiting lists can be several months or longer depending on your region. NICE guidance supports NHS prescription, but availability and speed of access varies widely across the UK.
Private route: Available through GPhC-registered online pharmacies and private clinics. A UK-licensed prescriber conducts an online clinical assessment and issues a prescription if appropriate. Mounjaro is dispensed directly and costs range from approximately £130–£320 per month depending on dose. Private access is typically faster (days rather than months) but you pay the full cost. Both routes require prescription and clinical assessment — Mounjaro is not available over-the-counter.
Check your local ICB website or contact your GP to understand NHS waiting times in your area before deciding between routes.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Is Mounjaro available on the NHS in the UK?
Yes, NICE has approved tirzepatide (Mounjaro) for NHS use in specialist weight management services (tier 3 and tier 4). However, availability varies by region. You'll need a GP referral to your local specialist service, and waiting lists can be lengthy. Mounjaro is not available in primary care (your GP cannot prescribe it directly).
What is the difference between "weight loss injections" and Mounjaro?
"weight loss injections" is informal UK slang for prescription weight loss injections — it refers to Mounjaro (tirzepatide), Wegovy (semaglutide), and other GLP-1 receptor agonist medications. Mounjaro is the brand name for tirzepatide, a dual GIP and GLP-1 agonist injection. All are prescription-only medicines.
What is the Mounjaro KwikPen and how does it work?
The KwikPen is Mounjaro's pre-filled injection device. Each pen contains four weekly doses. You inject yourself once a week, rotating injection sites (abdomen, thigh, or upper arm). The pen is simple to use and comes with clear instructions. Storage requires refrigeration until first use, then room temperature for up to 30 days.
How much weight can I expect to lose on Mounjaro?
Clinical trials (SURMOUNT-1) showed average weight loss of 15–21% of body weight over 72 weeks, depending on dose, alongside a reduced-calorie diet and increased physical activity. However, individual results vary significantly — some people lose more, some lose less. Your GP or prescriber can discuss realistic outcomes for you.
How do I get Mounjaro through the NHS?
Ask your GP for a referral to your local specialist weight management service (tier 3). They'll assess your eligibility based on BMI and health conditions. If approved, a prescriber will start you on Mounjaro and monitor your progress. Regional waiting lists vary — contact your local ICB for current timescales, or explore private options if NHS waiting times are lengthy.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.